1. Field of the Invention
This invention pertains to locking devices, and more particularly to apparatus that visually indicates the status of a locking device.
2. Description of the Prior Art
In our co-pending U.S. Patent application Ser. No. 667,653 filed Mar. 11, 1991, we describe in detail the structural and operational features of a lock for a moveable carriage of a mobile storage system. The carriage lock is manually operable to selectively enable or prevent a moveable carriage from rolling along rails embedded in a building floor. When the carriage lock is operated to an unlocked status, a person can manually rotate a handwheel located on the end of the moveable carriage. The handwheel is fastened to a hub, which, in turn, is mounted for rotation about the longitudinal axis of a shaft that is fixed to the moveable carriage frame. The hub mates with and drives a driver sprocket also rotatably supported on the shaft. A chain trained over the driver sprocket transmits power from the handwheel, hub, and driver sprocket to the axles and wheels that support the moveable carriage on the rails.
Referring to FIG. 1, reference numeral 1 indicates a typical prior handwheel used to manually drive a moveable carriage along floor rails. To prevent rotation of the handwheel 1 and thus prevent rolling of the moveable carriage along the rails, the carriage lock includes a pin, such as is described in U.S. Patent application Ser. No. 667,653, that is slidable within the hub 9 in directions parallel to the handwheel longitudinal axis 11. The pin is slidable between a first position whereat it is disengaged from a lock plate stationarily held to a fixed shaft, and a second position whereat it is engaged with the lock plate. With the pin in engagement with the lock plate, rotation of the hub 9 and thus of the handwheel is prevented, and the carriage is therefore unable to move. When it is desired to move the carriage, the carriage lock is operated such that the pin slides within the hub to become disengaged from the lock plate.
To slide the pin within the hub 9 between being engaged with and disengaged from the lock plate, the carriage lock further includes a locking knob 5 that is rotatable about the longitudinal axis 11 relative to the handwheel 1 and hub 9. The handwheel is formed with a central opening 3 that receives the locking knob 5. A peripheral flange 6 on the locking knob 5 is rather loosely captured between the handwheel adjacent the opening 3 and a face 7 of the hub 9, thereby retaining the locking knob in place. The locking knob 5 has limited rotation relative to the handwheel 1 and hub 9 about the longitudinal axis 11 between first and second angularly spaced end positions.
The locking knob 5 is also formed with a cam that engages the head of the pin. A spring in the hub 9 biases the pin against the locking knob cam. By rotating the locking knob between its first and second end positions, the cam acts to slide the pin within the hub between the pin first and second positions, respectively.
To enable a person to easily rotate the locking knob 5 between its first and second end positions, the locking knob is formed with a diametrically extending ridge 13. The person is able to grasp the ridge 13 with her fingers and thus rotate the locking knob without difficulty. In FIG. 1, it will be assumed that the solid lines 13 indicate the angular location of the ridge when the locking knob is in its first end position, and that the phantom lines 13, indicate the angular location of the ridge when the locking knob is in its second end position. Accordingly, the user of the mobile storage system is able to tell by looking at the position of the locking knob ridge relative to the handwheel 1 whether the mobile carriage is locked against movement or whether movement is permitted. Such knowledge of the status of the carriage lock is important to prevent a person from inadvertently attempting to force the handwheel 1 to move the moveable carriage when the handwheel is locked.
Although the prior carriage lock works very well, it nevertheless is subject to improvement. Specifically, it is considered desirable to enhance the visual indication given by the locking knob ridge 13 as to the status of the carriage lock.